3D-CMCC-CNR model

The 3D-CMCC-CNR is a process-based model that simulates forest growth and structure dynamics, as well as carbon, nitrogen, energy and water cycles at ecosystem scale on a daily time step. In the context of the scientific research on climate change, the model provides predictions on carbon sequestration in forest ecosystems, contributing to understand their mitigation role of climate effects.
Description
The 3D-CMCC-CNR model simulates the dynamics occurring in heterogeneous forests with different plant species, also if simultaneously composed by evergreen and deciduous, for different age, diameter, and height classes. The model is able to reproduce forests with a complex canopy structure constituted by cohorts competing with each other for light and water. The model simulates carbon fluxes, in terms of gross and net primary production (GPP and NPP, respectively), partitioning and allocation in the main plant compartments (stem, branch, leaf, fruit, fine and coarse root, non-structural carbon). In the recent versions, nitrogen fluxes and allocation, in the same carbon pools, are also reproduced. The 3D-CMCC-CNR also takes into account management practices, as thinning and harvest, to predict their effects on forest growth and carbon sequestration.
The 3D-CMCC-CNR is written in C-programming language and divided into several subroutines. To run the model, some input data are required. The meteorological forcing variables, on a daily time step, are represented by average, minimum and maximum air temperature, shortwave solar radiation, precipitation, vapor pressure deficit (or relative humidity). The model also needs some basic information about soil, such as soil depth and texture (clay, silt and sand fractions), as well as the forest stand information referred to plant species, ages, diameters, heights and stand density. An additional input is represented by species-specific eco-physiological data for the model parameterization.
History
The 3D-CMCC-CNR model has been implemented by Alessio Collalti at Euro-Mediterranean Center on Climate Change (CMCC), Division Impacts on Agriculture, Forest and Ecosystem Services (CMCC-IAFES); National Research Council of Italy (CNR), Institute for Agricultural and Forestry Systems in the Mediterranean (CNR-ISAFOM), and University of Tuscia. During the years, several improved versions of the model have been developed. In the early version of 2014 has been characterized by the addition of nitrogen dynamics, non-structural carbon (NSC) and simulation of the processes at daily time scale and the explicit simulation of autotrophic respiration. In the 5.3.3-ISIMIP version of 2018, the reproduction of atmospheric CO2 effects on the simulated processes and the dynamics related to plant mortality have been added explicitly as the effect of temperature acclimation of leaf photosynthesis to increasing temperature is accounted following Kattge & Knorr (2007) while for autotrophic respiration is based on Smith & Dukes (2013). In the current version (v.5.4), to simulate plant photosynthesis, the Light Use Efficiency (LUE) approach has been substituted by the Farquhar, von Caemmerer and Berry (FvCB, Farquhar et al., 1980) approach as implemented in the DePury and Farquhar method (however, both versions can still be used depending on the choice of the user). The photosynthesis rate depends on nitrogen content in the leaves and Rubisco, the temperature leading enzyme kinetics, the Maintenance Respiration and the difference between internal and external partial pressure of CO2.
Simulated processes
The main processes simulated by the model are constituted by:
* Photosynthesis, Farquhar, von Caemmerer and Berry (FvCB, Farquhar et al., 1980) approach as implemented in the DePury and Farquhar method;
* Carbon and Nitrogen allocation in different plant compartments (stem, branch, leaf, fruit, fine and coarse root, non-structural carbon);
* Autotrophic respiration, divided into maintenance and growth respiration components;
* Net Primary Productivity (NPP) is the result of GPP minus Autotrophic Respiration;
* Light and water competition among different forest canopy layers;
* Water balance, simulated by a soil bucket layer model;
* Plant mortality, due to three main causes: age, crowding competition and reserve depletions.
Future developments
To improve the simulation of carbon (C) and nitrogen (N) cycles in the soil, the 3D-CMCC SOIL module is under implementation. The module is constituted by a core that reproduces the key C- and N-dynamics related to litter and Soil Organic Matter (SOM) decomposition, transformation in more recalcitrant organic compounds (immobilization), nitrogen conversion in mineral form (mineralization), plant nutrient uptake, nitrogen input to the inorganic pool (symbiotic biological nitrogen fixation), CO2 emission in the atmosphere by heterotrophic respiration and the nutrient losses from the soil due to denitrification and leaching. The core will be subsequently integrated by the dynamics of root exudate production and mycorrhizae.
Projects and applications
The 3D-CMCC-CNR has been applied to several European sites constituted by Mediterranean, temperate, subalpine and boreal forests, involving several plant species, as Picea abies, Pinus laricio, Fagus sylvatica, Pinus pinaster, Pinus sylvestris, Quercus ilex, Quercus robur and Quercus cerris.
As at 2019 the model is involved in the following projects:
* MADAMES
* Landsupport-H2020
* The Inter-Sectoral Impact Model Intercomparison Project (ISIMIP)
* MEDSCOPE - MEDiterranean Services Chain based On climate PrEdiction
* OLIVE4CLIMATE
* CRESCENDO
* XF-ACTORS
In the past years the 3D-CMCC-CNR has participated to the following projects:
* ORIENTGATE
* KLAUS
* CIRCE
* CARBOTREES
* CarboItaly

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